3-Methyl-3,4-dihydro-9H-carbazol-1(2H)-one

In the title molecule, C13H13NO, the dihedral angle between the benzene ring and the fused pyrrole ring is 2.03 (5)°. The methyl group at the 3-position has an equatorial orientation. The cyclohexene ring adopts an envelope conformation. Three C atoms of the cyclohexene ring, with their attached H atoms, and all atoms of the methyl group are disordered over two positions, the site-occupancy factors being 0.883 (2) and 0.117 (2). In the crystal structure, molecules are stabilized by intermolecular N—H⋯O hydrogen bonds. A C—H⋯π interaction, involving the benzene ring, is also found.

In the title molecule, C 13 H 13 NO, the dihedral angle between the benzene ring and the fused pyrrole ring is 2.03 (5) . The methyl group at the 3-position has an equatorial orientation. The cyclohexene ring adopts an envelope conformation. Three C atoms of the cyclohexene ring, with their attached H atoms, and all atoms of the methyl group are disordered over two positions, the site-occupancy factors being 0.883 (2) and 0.117 (2). In the crystal structure, molecules are stabilized by intermolecular N-HÁ Á ÁO hydrogen bonds. A C-HÁ Á Á interaction, involving the benzene ring, is also found.
In the title molecule, C 13 H 13 NO, the dihedral angle between the benzene ring and the fused pyrrole ring is 2.03 (5)°.

Experimental
A solution of 2-(2-phenylhydrazono)-5-methylcyclohexanone (0.216 g. 0.001 mol) in a mixture of acetic acid (20 ml) and hydrochloric acid (5 ml) was refluxed on an oil bath pre-heated to 398 K for 2 h. The contents were then cooled and poured into cold water with stirring. The brown solid which was separated by passing through a column of silica gel and eluted with a (98:2, v/v) petroleum ether-ethyl acetate mixture to yield the title compound (0.148 g, 74%). This was recrystallized from ethanol.

Refinement
Atoms C2A, C3A, C4A of the cyclohexene ring, with attached hydrogen atoms, and all atoms of the methyl group are disordered over two positions; the site occupancy factors refined to 0.883 (2) and 0.117 (2). The H atom bonded to N9 was located in a difference Fourier map and refined isotropically. Other H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.95-1.00 Å and U iso (H) = xU eq (parent atom), where x = 1.5 for methyl and 1.2 for all other carbon-bound H atoms.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound, showing the atom-numbering scheme and displacement ellipsoids drawn at the 50% probability level. H atoms are shown as small spheres of arbitrary radius. Only the major disorder component is shown.